Sound + Vision
Some things just go together. Brie and apple pie, for example—sounds wierd, right? Just take a bite. It tastes like fucking magic. That's because if you get past the idea of what "pie" and "Brie" are supposed to be, you're really talking about two closely associated foods—fruit and cheese.
Same thing happens when music gets mashed with cartoons. Hard to explain. Heaven on earth.
If you break it down, illustration and music are tools we've developed to consciously act out our subconscious. When you put them together, they telescope into each other the same way our dreams do. Sound is really effective at wedging into our sleep and mutating dream images to wrap around it. In turn, what we see in our dreams gives the sound meaning and significance that wouldn't exist outside of that dreamstate. And on and on like a mobius strip.
But here we are again. It's kind of pointless to try to to explain it. I'd rather just show you these, which I love dearly.